The present invention relates to a patch for application to the skin to perform some determined treatment, for example a cosmetic treatment with active substances being released to perform some given action on the epidermis.
Numerous patches of that type are known, and in general they present a multilayer structure comprising an adhesive matrix based on one or more polymers designed on one face to come directly into contact with the skin and on the other face to be attached to a backing.
The invention relates more particularly to patches in which the matrix presents adhesive properties when in the dry state.
In such patches, the matrix advantageously contains one or more active substances to be released on the epidermis to exercise a given effect, for example a hydrating or regenerating action.
Such active substances can be released by wetting the skin before applying the patch.
In a variant, the water for putting into solution the active substances contained in particular at the surface of the matrix can come from the region of the skin that is situated beneath the patch, in which case it is preferable to use a backing that is occlusive so as to favor local transpiration.
Known patches do not give entire satisfaction.
In particular, the quantity of water deposited on the skin prior to application of the patch can turn out to be insufficient to put the active substances contained in the matrix into solution as described.
In addition, an occlusive backing can be rather uncomfortable in use, providing a heating effect rather than a cooling or freshening effect.
Consequently, there exists a need to further improve the conditions under which one or more active substances are applied to the skin by means of a patch.
The present invention provides a novel patch of the type comprising a matrix having adhesive properties in the dry state and containing at least one active substance, said matrix being attached via one face to a backing and being for application via its other face to the skin, wherein said backing is selected in such a manner as to be capable of containing a predetermined liquid suitable for dissolving at least in part the active substance(s) contained in the matrix, and wherein said matrix is permeable to the liquid.
Thus, by means of the invention, the liquid (which can be water or any other solvent) can diffuse towards the skin through the matrix from the backing which then constitutes a kind of reservoir, and this presents multiple advantages.
Firstly, as it diffuses through the matrix, the liquid causes the above-mentioned active substance(s) to pass into solution, thereby releasing the substance(s) from the matrix.
The matrix can act like a xe2x80x9cwickxe2x80x9d tending to absorb the liquid impregnating the backing by capillarity, and it can also act like a xe2x80x9cfilterxe2x80x9d by retaining particles while allowing dissolved active substances to pass through.
In addition, in particular when the liquid is water and the patch is applied on wet skin, the water-impregnated backing serves to retard drying of the interface with the skin and thus behaves as a kind of occlusive backing, while avoiding the drawbacks specific to using an occlusive backing, in particular the drawbacks concerning user comfort.
Fluid flow can also be established between the interface with the skin and the liquid-impregnated backing, which is favorable for the breathing of the skin and for renewing the active substances that come into contact with the skin and/or for eliminating to the backing any impurities or toxins that can be released at the interface with the skin.
Finally, the thermal inertia of the soaked backing and the evaporation of the liquid from its surface gives the user a feeling of coolness or freshness which further increases user comfort.
In a preferred implementation of the invention, the matrix comprises one or more polymers which may be elastomers.
The liquid used for impregnating the backing can be water or an aqueous or alcohol solution, in which case the matrix preferably includes at least one hydrophobic polymer.
The backing is advantageously constituted by a porous matrix, e.g. a non-woven cloth.
The active substance(s) contained in the matrix can be cosmetically active compounds, preferably hydrosoluble compounds, and can be dispersed in the matrix in particulate form.
The cosmetically active compound(s) is selected, for example, from: emollients, moisturizers, healing agents, regenerating agents, anti-wrinkle agents, tightening agents, anesthetics, sun screens, soothing agents, self-tanning agents, brightening agents, concealers, grease reducers, and mixtures thereof.
In a preferred implementation of the invention, the matrix also contains in dispersion a filler of particles of at least one liquid-absorbing compound, e.g. a water-absorbing hydrophilic compound when the liquid used is water or an aqueous solution or an alcohol solution.
The water-absorbing compound is then selected, for example, from the following list: superabsorbent crosslinked polyacrylates having a large swelling factor in water, polyvinyl alcohol, carboxyvinyl polymers, semi-synthetic derivatives of cellulose, starches, biogums, biosaccharides, scleroglucanes, casein, photocolloids such as alginates, gelatin, cotton fibers, gellanes, xanthanes, laponite, silicas, or mixtures thereof. By way of example, the liquid-absorbing compound filler is at a concentration lying in the range 0.2% to 50% by weight, preferably in the range 1% to 20%, more preferably in the range 1% to 10%, relative to the total weight of the matrix.
Preferably, the content in the matrix of liquid-absorbing compound(s) is selected so that the quantity of liquid that can be absorbed by said compound(s) is greater than or equal to the quantity of liquid required for dissolving the active substance(s) contained in the matrix.
The matrix may have gaps, e.g. microperforations for making the matrix permeable to the liquid in which the backing is soaked and/or for favoring the exchange of gas and/or liquid between the backing and the interface with the skin.
The matrix can be deposited on the backing in a grid pattern or the like.
The matrix can contain at least one active substance capable of reacting chemically with the liquid used.
In a particular embodiment, the patch is contained in a hermetically sealed package and the backing is already impregnated by a liquid.
The invention also provides a kit constituted by a patch as defined above together with a receptacle containing a liquid for impregnating the backing attached to the matrix.
The liquid can include at least one active substance for exercising a predetermined effect on the skin, which effect can be cosmetic or otherwise, for example an anesthetic.
The invention also provides a method comprising the steps consisting in:
supplying a patch as defined above; and
impregnating the backing with a determined liquid before or after application to the skin.
In a particular implementation of the method, the skin is wetted prior to the patch being applied thereto.
The quantity of water soaking the backing per unit area of the backing is preferably greater than the quantity of water deposited on the skin per unit area.
The patch is left on the skin, for example, for a length of time lying in the range 5 minutes (min) to 60 min.